Reverse acting pneumatic amplifier



June 23, 1964 wALLER 3,138,168

REVERSE ACTING PNEUMATIC AMPLIFIER Filed Jan. 12, 1962 I so INVENTOR John E Waller ATTORNEY United States Patent '0 7 3,138,168 7 REVERSE ACTING PNEUMATIC AMPLIFIER John F. Waller, Philadelphia, Pa., assignor to Robertshaw- Fulton Company, a corporation of Delaware Filed Jan. 12, 1962, Ser. No. 165,780 r 8 Claims. (Cl. 137-82) This invention relates to pneumatic amplifiers and more particularly, to a pneumatic amplifier wherein an increase in the input signal results in a decrease of the output signal.

It is an object of this invention to provide a pneumatic amplifier where large changes in output pressure are provided by small changes in input pressure.

Another object of the present invention is to provide a pneumatic amplifier having high gain characteristics wherein the change in output pressure is inversely proportional to a change in input pressure.

Still another object of this invention is to provide a pneumatic amplifier of the reverse acting type wherein a novel single diaphragm and integral flapper combination provides the only active element.

These and other objects of this invention will become apparent with reference to the following specification and drawings which relate to a preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a schematic cross-section of the invention; and

FIGURE 2 is a top plan view of FIGURE 1.

Referring now to the drawings, the pneumatic amplifier 10 is shown to include a hollow cylindrical casing or housing 12 comprising two interlocked housing portions hereinafter referred to as the base 14 and the end cap 16.

The base portion 14 includes an internal peripheral shoulder 18 on which is mounted the peripheral flange 20 of a flexible diaphragm 22. The upper end of the base portion 14, as shown, is open and of a size to'internally receive the lower end of the end cap 16. The upper end of the said base 14 from the shoulder 18 comprises a thin walled extended portion 24.

The end cap is also shaped like a hollow cylinder with I the inner end 26 thereof dimensioned to abut a peripherally disposed gasket or compression ring 28 in juxtaposition with the peripheral flange 20 of the diaphragm 22 on the side thereof opposite the shoulder 18.

A second shoulder 30, centrally located in the base 14, circular in shape and concentric with the peripheral shoulder 18, is provided on the end face of a centrally located upstanding cylindrical collar 32 having a bore'34 longitudinally thereof.

The diaphragm 22 has a bore 36 at the center thereof in registry with the bore 34 in the collar 32. A second or inner peripheral flange 38 about the central bore 36 is provided and is anchored by any suitable means (not shown) to the second shoulder 30 on the collar 32.

The entire housing 12 is maintained/in assembled position by crimping the thin walled exte ifsion 24 of the base 14 over a cooperating external flange or shoulder 40 on the lower end of the end cap 16. This crimping step also secures the outer peripheral flange 20 of the diaphragm 26) between the first shoulder 18 of the base 14 and the compression ring 28.

The diaphragm 22 forms an upper or reference pressure chamber 42 and a lower or signal chamber 44 with the end cap 16 on one side and base '14 on the other, respectively. A centrally located exhaust port 46 is provided in the end cap 16 for venting the upper chamber to atmosphere. A signal inlet line 48 having an inlet flow port 50 therein is provided in the base 14 to couple the signal input chamber 44 to the said input signal source.

3,138,168 Patented June 23, 1964 ice A nozzle 52 is press-fitted in the bore 34 of the central collar 32 in the base 14. The nozzle 52 extends through the bore 36 in the diaphragm 22 such that the mouth or outlet orifice 54 of the nozzle 52 extends above the diaphragm 22.

Integral with the diaphragm 22 is a hood-like flapper 56 which is bridged across the nozzle mouth 54 to normally maintain the said mouth closed when the diaphragm 22 is in a natural, non-distorted condition.

The flapper 56 generally comprises an inverted dishshaped structure which is rigid in comparison to the diaphragm 22. The diameter of the dish is such that the peripheral flange 58 thereon is affixed to the diaphragm 22 along a line of substantially maximum distortion of the diaphragm in response to pressure dilferentials between the inlet and reference chambers 44 and 42, respectively. A plurality of flow ports 66 are provided in the dish bottom or flap valve 62 of the flapper 56.

The nozzle 52 is fed from a line 64 comprising one leg of a T-connection 66. The through-connection of the T is a flow restriction 68 in a line 70 which is connected with a source of operating or supply pressure (not shown).

The branch connection of the T comprises an output line or port '72 between the nozzle 52 and the flow restriction 68.

Operation With the input line 48 connected to a signal pressure source (not shown), the output line or port 72 connected to a pressure receiyer (not shown), and the supply line 70 with the flow restriction 68 therein connected to a pressure supply (not shown), the operation of the pneumatic amplifier 1% will now be described.

In the absence of an input signal pressure in the input signal chamber 44, there is no pressure differential across the diaphragm 22. Thus, there is no force tending to distort the diaphragm 22 other than that generated over the small area of contact between the mouth 54 of the nozzle 52 and the valve plate 62 of the flapper 56. This force is of a negligible magnitude with respect to that required to distort the diaphragm 22 and is distributed to the diaphragm 22 over the entire area of the peripheral flange 58 of the flapper 56.

Thus, in the pressure line 64 feeding the nozzle, a back pressure is built up, in the absence of a signal input, which is equal to the supply pressure and this pressure is reflected at the output port '72 and conveyed to a suitable pressure receiver. The initial condition of no signal pressure at the input is, therefore, in inverse relationship with the output of the amplifier 10 which is the maximum or supply pressure at the output port 72. 7

When an input signal pressure is transmitted to the input chamber 44 via the inlet flow port 50, the flexible diaphragm 22 will be distorted by a force proportional to the input pressure and will, therefore, displace the valve plate 62 of the flapper 56 away from the mouth 54 of the nozzle 52 a distance directly proportional to the input signal pressure in the input chamber 44.

The back pressure in the pressure line 64 between the nozzle mouth 54 and the flow restriction 68 varies in inverse proportion to the distance of the valve plate 62 of the flapper 56 from the nozzle mouth 54. This is the result of a decreasing impedance to flow from the nozzle mouth 54 as the distance of the flapper 56 therefrom is increased. The fluid flow from the nozzle passes through the flapper flow ports 60 into the upper or reference chamber 42 and out through the exhaust port 46 to atmosphere.

Since the back pressure in the pressure line 64 is reflected at the output port 72, the output pressure is inversely proportional to the signal input.

Because of the relatively small area on the flapper 56 against which fluid flow from the nozzle 52 acts and because of the relatively very large area of the diaphragm chamber 44, the operating or supply pressure may be made very high with respect to the signal pressure, whereby a very high gain is made possible with the pneumatic amplifier 10.

7 By using difierent size flow restrictions 63 and/or different size nozzle orifices 54, the operating characteristics such as sensitivity and speed of response may be selectively varied. Thus, the nozzles 52 may be removably mounted in the bore 34 of the collar 32 rather than pressfitted, to facilitate the ready removal and selective replacement thereof.

As can be'seen from the foregoing specification and drawings, this invention provides a reverse acting pneumatic amplifier having only a single novel active element therein and is capable of high gain and selectively adjustable operating characteristics. In addition, the low mass of the active part therein substantially eliminates sensitivity to the physical position of the amplifier.

It is to be understood that the embodiment shown and described herein is for the purpose of example oniy and is not intended to limit the scope of the appended claims.

What is claimed is:

1. Reverse acting pneumatic amplifier means comprising a housing, a flexible diaphragm centrally and peripherally anchored on said housing and forming a chamber therewith, signal pressure input means for said chamber, a nozzle in said housing, flap valve means integral with said diaphragm intermediate the anchored portions thereof in.

flow preventing juxtaposition with said nozzle when said diaphragm is in a natural undistorted condition, a source of supply pressure, a pressure line connecting said nozzle with said source of supply pressure, and an output port in said. pressure line, said flap valve normally acting to create a back pressure in said pressure line substantially equal to thesupply pressure in the absence of a signal pressure input and said diaphragm, upon the reception of a signal pressure input to said chamber, acting to distort and move said integral flap valve means away from said nozzle a distance proportional to the increase in said input signal pressure to permit increased flow from said nozzle and thereby cause a proportionate decrease in back pressure in said pressure line, whereby the pressure at said output port is inversely proportional to the input signal pressure.

2; The invention defined in claim 1, wherein said nozzle extends through said chamber and out through said diaphragm at the centrally anchored portion thereof and is sealed from said chamber and wherein said flap valve means comprises an inverted dish-shaped plate enclosing the mouth or" said nozzle, a flange on the said plate integral with said diaphragm along a line through the flexible portion of said diaphragm, and a plurality of flow ports in said plate.

3. The invention defined in claim 1, wherein said amplifier further includes a flow restriction located in said pressure line between said output port and said source of supply pressure.

4. The invention defined'in claim 1, wherein said housing includes a peripherally disposed internal shoulder for securing the outer periphery of said diaphragm, a centrally located collar, a bore in said collar extending through said housing, a central aperture in said diaphragm in. registry with said bore, and a shoulder on said collar for securing the central portion of said diaphragm about the periphery of said aperture.

5. Theinvention defined in claim 4, wherein said nozzle is mounted in the said bore in said collar and extends through said aperture in said-diaphragmand wherein said' flap valve means comprises an inverted dish-shaped plate enclosing the mouth of said nozzle, a flange on the sad plate integral with said diaphragmalong a line in the region between said shoulders, and a plurality of flow ports in said plate. 6. The invention defined in claim 4, wherein saidamplifier further includes a flow restriction located in said pressure line between said output port and said sourceof supply pressure.

7. In a pneumatic amplifier, in combination, a flexible diaphragm anchored at the peripheral and central portions thereof, an' aperture inthe central anchored portion of said diaphragm, a nozzle extending through said aperture,

and a flap valve means integral with said diaphragm enclosing said nozzle and normally juxtaposed with the mouth thereof to prevent flow therefrom, said flap valve means being mounted on said diaphragmbetween said central and peripheral anchored portions. I

8. The invention defined in claim 7, wherein said flap valve means comprises an inverted dish-shaped plate enclosing the mouth of said nozzle, a flange on said plate integral with said diaphragm along a line through the flexible portion of said diaphragm, and a plurality of flow ports in said plate. g I

References Cited in the file of this patent UNITED STATES PATENTS 2,073,838

Hammond et al Mar. 16, 1937 2,451,451 Tate Oct. 12,- 1948 

7. IN A PNEUMATIC AMPLIFIER, IN COMBINATION, A FLEXIBLE DIAPHRAGM ANCHORED AT THE PERIPHERAL AND CENTRAL PORTIONS THEREOF, AN APERTURE IN THE CENTRAL ANCHORED PORTION OF SAID DIAPHRAGM, A NOZZLE EXTENDING THROUGH SAID APERTURE, AND A FLAP VALVE MEANS INTEGRAL WITH SAID DIAPHRAGM ENCLOSING SAID NOZZLE AND NORMALLY JUXTAPOSED WITH THE MOUTH THEREOF TO PREVENT FLOW THEREFROM, SAID FLAP VALVE MEANS BEING MOUNTED ON SAID DIAPHRAGM BETWEEN SAID CENTRAL AND PERIPHERAL ANCHORED PORTIONS. 